Softening is the process of removing Calcium and Magnesium ions from water through Cation exchange. This is typically used to reduce scaling tendency of water used for boiler feed, or to increase the lather effect of detergents, particularly in laundries & process, Calcium and Magnesium ions in solution are exchanged for sodium ions attached to a cationic resin. When water is passed through this resin, the calcium and magnesium ions in the water displace the Sodium Ions, and adsorb onto the resin. During the regeneration process, a highly concentrated saline solution (15-30% NaCl) is used to “wash” the resin. This causes the Ca or Mg which is adsorbed on the resin to be replaced with Na.
Sizing of Softener is based on three factors; the capacity of the softener (flow rate), feed water hardness, and frequency of regeneration required.